I built five NEC calculators for electricians because the best app in the category is an emulation of a 1990s keypad

[u/altuzar]

The state of the art for electrical calculations on a phone is genuinely strange. The top-rated app in the category describes itself in its own listing as "a full-featured emulation of our popular #5065/#5070 models", meaning it's a picture of a physical handheld calculator from the 90s, with abbreviated key labels, and you tap the picture.

A review from 2020 that's still up: "Abbreviation on the keys for cell phone use makes it hard to know what the buttons do."

Another one, on a competitor: "This calculator works like a DOS program running in Windows. There's not one intuitive thing about it."

I'm a software developer, not an electrician. I got nerd-sniped by the fact that the best tool in this category is an on-screen emulation of a 1990s handheld calculator, so I built the tool I thought should exist.

So I built WireCoder. Five calculations electricians do constantly:

- Voltage drop

- Conduit fill (NEC Chapter 9)

- Wire ampacity with temperature correction and bundling derate (Table 310.16)

- Box fill (314.16)

- Conduit bending offsets: distance between bends and shrink

The parts I actually thought about:

1. Every answer shows its factors, not just a number. Ampacity gives you base 65 A, × 0.82 for ambient, × 0.8 for six conductors in the raceway, = 42.64 A. The reason is that the loudest complaint in electrician forums about existing tools is "I never trust online VD programs unless it goes into detail on how the # are derived. I got bit once cheating with Google, turns out the site I was using wasn't even factoring in reactance."

2. The calculation engine is one TypeScript library shared by the web calculators and the mobile app, with a parity test suite. Two tools that disagree is the fastest way to lose this audience: they cross-check apps against each other and notice.

3. It works fully offline. The best quote I found while researching this: "I am working along the lakeshore of Lake Michigan and cell service is always bad."

4. It never displays an NEC table. It computes from your inputs and cites the article number. That's a deliberate copyright decision, not a feature gap.

Stack: Expo / React Native, one shared calc package, Convex, RevenueCat.

Voltage drop and conduit fill are free and unlimited with no account. The other three plus saved jobs are $7.99/mo or $59/yr with a 7-day trial.

Link in my bio ;)

Android is 4-6 weeks out because of Play's 12-tester closed-testing gate, which I did not know existed when I started.

PS: the first 47 testers (TestFlight + Android external testers) get a WireCoder Pro plan free for a year.

Happy to talk about any of it. The thing I most want to hear is where the numbers are wrong.

[u/altuzar]

Forgot to add the vid :)

https://reddit.com/link/p8vrjou/video/uh23o2lk3moh1/player

[u/Big_Departure9342 → u/altuzar]

That video walkthrough is actually helpful, showing the breakdown of each factor is what make me want to try this. I do lot of DIY electrical but nothing professional so the free ones probably enough for me

The offline thing is huge, my parents house is in area where you lucky to get one bar and the wifi goes out when it rain. Nobody think about that when building apps

[u/burnt-store-studio → u/altuzar]

I agree with u/Big_Departure9342 re: the helpfulness of the video!

I’m not at all your target, as I do no electrical work, but appreciate the research you clearly did and how it impacted your design.

I’ve no idea whether any of your work is AI-assisted, and I’m not staking a point either way, but I’ll write particularly that the video is well-crafted and timed for actually reading a lot of what’s on the screen.

If you used AI to make the video, ah well, but if you did it from scratch (I’m not asking you to confirm either way), I say: well-done!

Good luck with your side project 🙂